Stem cells continue to be of enormous scientific and clinical interest, due to the myriad therapeutic possibilities promised by their use. The initial excitement generated by identification of novel stem cell populations has given way to more focused effort on methods to manipulate their differentiation and self-renewal capacities. A number of genome-scale studies are now underway to catalog stem cell gene expression profiles or generate mouse mutants in stem cell-control genes. Coupled with more classical single gene or pathway approaches to stem cell biology, by 2005, some of the nuts-and-bolts of stem cell function should begin to be revealed. Such fundamental understanding will provide the foundation for more rapid advances toward the clinic. This conference will bring together top stem cell biologists, particularly in the areas of embryonic, neural, and hematopoietic stem cells, to discuss molecular mechanisms of stem cell function.